EP1266917A1 - Waterdilutable, etherified melamine-formaldehyde resins - Google Patents

Abstract

A water-dilutable etherified melamine-HCHO resin obtained by reaction of melamine, HCHO, a compound with anionic groups and an etherifying alcohol in a ratio of 1 : (1.7-7) : (0.01-0.4) : (5-30). <??>Also included are Independent claims for preparation of the resin.

Description

The invention relates to water-dilutable etherified melamine-formaldehyde resins, the Manufacture and use for the production of building materials and insulation material, Nonwovens manufacturing, paper and textile equipment and production of foils and edges.

The production of water-soluble etherified melamine resins is generally known. First, melamine is used at pH values from 7 to 10 and temperatures from 40 to 110 ° C (optionally in a mixture with other aminoplast formers such as urea, dicyandiamide, Acetoguanamine, benzoguanamine and caprinoguanamine) by adding formaldehyde or methylol-releasing these under the reaction conditions and condensed, then the etherification alcohol is added and at pH values of 1 to 7 implemented at temperatures of 30 to 80 ° C. The condensation and Etherification conditions depend on the properties desired for the resin such as e.g. Viscosity and water dilutability. As ethereal alcohol, methanol, Ethanol, n- and iso-propanol and the isomeric butanols (n-, sec.-, tert.- and iso-butanol) preferred, especially methanol, n-butanol and isobutanol.

The preparation of anionically modified melamine resins, i.e. Cocondensates Melamine, formaldehyde, salts of amidosulfuric acid (sulfamic acid, sulfamic acid, Amidosulfonic acid), sodium sulfite or sodium bisulfite (sodium bisulfite) and others. is also known.

For example, EP-A 0 176 709 (DE-A 34 30 248) describes condensates produced by reacting melamine, formaldehyde (molar ratio M / F = 1: 2 to 1: 3.2 mol / mol), a sulfamate (0.025 to 0.045 mol of sodium sulfamate per 1 mol of formaldehyde; corresponding to 0.05 to 0.14 mol of the sulfamate per 1 mol of melamine) and a non-reducing sugar (in an amount of at least 3% of the mass of the reaction mixture) in the presence of a (thio- ) Amides or amidines and a C ₁ - to C ₃ alcohol at a pH value above 8. The resins obtained serve as coating, impregnating and binding agents for nonwovens. The resin solutions should have a particularly good storage stability. Under the specified alkaline reaction conditions - pH higher than 8 - and the small amounts of alcohols added - in the examples given below 0.35 mol methanol to 1 mol melamine - etherification is excluded. The water dilutability of the resins described is below 1: 7 (measured as the mass ratio of resin solution to deionized ("demineralized") water), and unlimited miscibility with demineralized water is not achieved.

DE-A 22 59 680 describes a process for the production of organic Aminocarboxylic or aminosulfonic acids or sodium or ammonium sulfite or hydrogen sulfite modified and etherified with alcohols containing 1 to 3 carbon atoms Melamine-urea-formaldehyde resins with a mass ratio of melamine to Urea from 1: 9 to 9: 1 claimed. The resins are used as a chlorine-based finishing agent used. The amino groups of melamine and urea must be complete be methylolated; the condensation products should preferably not contain any free NH groups included more. The process has two stages: first, under alkaline catalysis methyloliert and the anionic component condensed, then with Alcohol etherified under acid catalysis. Resins with such a high Degree of methylolation result in products with increased formaldehyde elimination during Dry.

In US-A 3,487,048 (GB 1232031) the methylolation and etherification of melamine described in one step in acidic medium. For this, 3 to 6 mol of formaldehyde are added Methanol with melamine with the addition of acids, preferably amidosulfonic acid, as Catalyst converted directly to a methyl etherified melamine resin in one step. The added amidosulfonic acid only serves as a proton donor, an incorporation into the resin will not described or required for resin properties. The one used in the examples The amount of amidosulfonic acid is 1.3 to 1.4 mmol per 1 mol of melamine. The problems of Water dilutability and storage stability are not addressed.

The release of formaldehyde during the hardening of etherified (with methanol) Melamine resins can be reduced by changing the molar ratio F / M from Choose formaldehyde to melamine as low as possible. On the other hand the lower limit for the F / M ratio due to the solution properties of melamine the methylolation determined. For resins with an F / M less than 1.9, it is difficult to longer-lasting resins with a high level that remains stable over the storage period To maintain water compatibility. It is also possible to use unetherified melamine resins an F / M of less than 2 to achieve an unlimited Water compatibility with sulfamates or sulfites or bisulfites (hydrogen sulfites) were modified. The durability of these resins with more stable over the storage period high water tolerance is limited to just a few weeks.

It is the object of the invention to provide such aqueous melamine resins which at the same time good storage stability and unlimited water miscibility at low Have formaldehyde cleavage of the soaked or finished substrates.

Aqueous melamine resins are those melamine resins which have a mass fraction of water of at least 5%. These become "unlimited water miscible" Melamine resins referred to in the system consisting of melamine resin and water Room temperature (20 ° C) have no mixture gap. This can be done macroscopically There is a mixture gap due to the formation of a turbidity (opacity) during the gradual Recognize dilution of the pure melamine resin with water with intensive mixing. Aqueous melamine resins which are at least 6 weeks after are considered to have a good shelf life show no segregation (turbidity) during their production.

Etherified by condensation of compounds with anionic groups in (methyl) Melamine-formaldehyde resins were able to develop new resins with significantly improved storage stability can be obtained with unlimited water miscibility.

Compounds with anionic groups are understood to mean those which dissolve of the modified melamine resins in water or aqueous systems Dissociation of melamine resins dissolved or dispersed in water gives the anionic Contain groups in condensed form.

The invention relates to water-dilutable etherified melamine-formaldehyde resins which can be prepared by reacting melamine, formaldehyde, a compound with anionic groups and a etherifying alcohol with a molar ratio in the reaction mixture of melamine: formaldehyde: compound with anionic group: etherifying alcohol of 1: (1 , 7 to 7.0): (0.01 to 0.4): (5 to 30), where the compounds with anionic groups preferably from salts of sulfamic acid (sulfamic acid, amidosulfuric acid, H ₂ N-SO ₂ -OH), the sulphurous acid (H ₂ SO ₃ , HO-SO-OH) and the pyro-sulphurous acid (disulphurous acid, H ₂ S ₂ O ₅ , HO-SO-O-SO-OH) with alkali metals and ammonium.

Through the reaction until the reaction is complete or almost complete, a Obtained resin that is derived from the compounds mentioned in the building blocks contains the specified molar ratio. A reaction becomes almost complete referred to, in which the degree of implementation at least 80%, preferably at least 82% and is in particular at least 85%.

Melamine is preferably used as the only aminoplast former, but it is also possible up to 10% of the melamine selected by one or more compounds To replace acetoguanamine, benzoguanamine and caprinoguanamine. Urea and / or Dicyandiamide and / or thiourea should not or only in mass fractions of maximum 8%, based on the total mass of the aminoplast formers, are used. Is preferred it, at most 7%, and particularly preferably, at most as 6% (thio) urea or Use dicyandiamide, in particular this mass fraction should not exceed 5%. It is possible, however, cyclic ureas such as ethylene urea (2-imidazolidinone), propylene urea (2-oxohexahydropyrimidine) or glycoluril in mass proportions of up to 10% use, based on the total mass of the aminoplast.

Linear or branched aliphatic alcohols with 1 to 6, preferably 1 to 4 carbon atoms are used individually or in a mixture. Prefers are methanol, ethanol, n- and iso-propanol, n-butanol and isobutanol; especially methanol is preferred.

Suitable compounds with anionic groups are those under the conditions the condensation of melamine and formaldehyde by participating in the Condensation reaction or by another reaction with melamine, formaldehyde or the condensation products of melamine and formaldehyde in the resulting resins be installed and dissociate when the resin is dissolved in water so that in the Resin molecules are formed and the cationic components of the anions mentioned Dissociate compounds as a cation in the aqueous solution. As connections with Anionic groups are particularly preferred the sodium salt of amidosulfuric acid and the sodium disulfite (sodium pyrosulfite, sodium metabisulfite).

Another object of the invention is a process for the production of etherified Melamine resins, which are produced in two stages: first, in the presence the connection with an anionic group melamine and formaldehyde under alkaline Conditions implemented, then the resulting resin solution Etherification alcohol, preferably methanol, and an acid are added and the etherification until to the desired degree of etherification.

It is also possible according to the invention to first form the compound with an anionic group the second stage, after dissolving the melamine in the aqueous formaldehyde solution (i.e. i. after the onset of the methylolation reaction) or after completion of the Add methylolation reaction. In any case, this connection should still be added during the alkaline condensation phase. The condensation is still to continue until the content of unreacted compound with anionic Group has dropped to 15% or less of the concentration used. After that the reaction solution is acidified and the etherification is connected as a third stage.

In all cases, the tolerability of the Reaction mixture with saturated saline can be used. Preferably the etherification should be carried out until the tolerance of the Reaction mixture with the saturated saline solution is at least 1: 2.0. The Compatibility is determined so that with an intimate mixture of a mass part of Reaction mixture with x parts by mass of the saturated saline solution a homogeneous Mixture is obtained without visible turbidity. The mass of added Saline solution increased by further addition of this solution, the mixture obtained stirred again and assessed visually. If there is still no clouding, more will appear Saline added etc. As tolerance 1: x the ratio of the mass of (inserted) reaction mixture and saline called, in which a permanent Turbidity occurred.

The resins thus obtained are suitable for use in the production of building materials, Insulation materials, nonwovens, paper and textile equipment and manufacture of Foils and edges. Mineral substances such as glass wool, rock wool, papers, Decorative papers, cardboard boxes, textile structures such as fabrics, scrims, knitted fabrics, felts, nonwovens, each made of fibers or threads of glass, natural fibers, fiber-forming natural and synthetic polymers such as cellulose, polyamides, polyesters, polyacrylonitrile or Polyolefins impregnated or coated with aqueous solutions containing these resins. Then the impregnated or coated fabrics are dried as well if necessary, cut to the desired shape or length.

The resins according to the invention are particularly suitable for finishing papers and in the bonding of glass fiber fleeces.

In the following examples, as in the previous text, all information means with the unit "%" mass fractions (quotient of the mass of the substance in question and the Mass of the mixture), unless stated otherwise. Concentration figures are in "%" Mass fractions of the solute in the solution (mass of the solute divided by the mass of the solution).

Example 1:

In a 4 1 three-necked flask with stirrer, reflux condenser and internal thermometer 73 g of deionized (desalinated) water and 499 g (3.6 x 1.8 mol) of a 39% aqueous solution Formaldehyde solution submitted and heated to 85 ° C. Then 3.6 ml of 2.0 N (3.6 x 2.0 mmol) sodium hydroxide solution, 214 g (3.6 x 0.2 mol) of a 40% aqueous solution Sodium sulfamate solution - a pH of approx. 8.7 was set - and immediately afterwards 454 g (3.6 mol) melamine added. The approach was supported by the heat of reaction heated to 95 ° C within 5 minutes and another 10 minutes at 95 ° C touched. Then it was cooled to 58 ° C. 2307 g (3.6 x 20.0 mol) of methanol and 9.4 g (3.6 x 22.0 mmol) of 53% nitric acid were added. It posed a pH of approx. 6.3. The reaction mixture was heated to 50 ° C, it was kept under stirring at this temperature until the compatibility of the Reaction mixture with saturated saline at 20 ° C 1: 5.0 (mass ratio of Reaction mixture and the saline) was. The reaction was then by addition of 40 ml (3.6 x 22 mmol) of 2 N sodium hydroxide solution and cooling to 30 ° C. The The reaction mixture containing methanol was removed on a rotary evaporator at 100 hPa (100 mbar) at a bath temperature of approx. 60 ° C and then by adding deionized water to a solids mass fraction of 75% (sample weight 2 g, Drying for 1 hour at 120 ° C in a glass bowl) set. The pH the resin solution was adjusted to 10 by adding dilute sodium hydroxide solution. It were 972 g resin with a solids mass fraction of 75%, a viscosity at 23 ° C. of 2020 mPa · s and unlimited compatibility (miscibility) with deionized Get water. The content of free sodium sulfamate in the resin was (measured by Ion chromatography) approx. 0.09%. This was less than 1% of the used Sodium sulfamate free before. The resin had a shelf life of more than 2 Months.

Example 2:

170 g of deionized water and 499 g (3.6 x 1.8 mol) of a 39% strength aqueous formaldehyde solution were placed in a 4 1 three-necked flask equipped with a stirrer, reflux condenser and internal thermometer and heated to 85.degree. Then 3.6 ml of 2.0 N (3.6 x 2.0 mmol) sodium hydroxide solution, 68.4 g (3.6 x 0.1 mol) sodium disulfite (Na ₂ S ₂ O ₅ ) and immediately thereafter 454 g (3.6 mol) melamine added. Supported by the heat of reaction, the mixture was heated to 95 ° C. in the course of 5 minutes and stirred at 95 ° C. for a further 25 minutes. Then it was cooled to 58 ° C. 2307 g (3.6 x 20.0 mol) of methanol and 9.4 g (3.6 x 22.0 mmol) of 53% nitric acid were added to the reaction mixture. This resulted in a pH of approximately 6.7. The reaction mixture was heated to 50 ° C., the mixture was kept under stirring at this temperature until the compatibility of the reaction mixture with saturated sodium chloride solution at 20 ° C. was 1: 5.0 (mass ratio of the reaction mixture and the sodium chloride solution). The reaction was stopped by adding 36 ml (3.6 × 20 mmol) of 2N sodium hydroxide solution and cooling to 30 ° C. The methanol-containing reaction mixture was concentrated on a rotary evaporator at 100 hPa (100 mbar) at a bath temperature of approx. 60 ° C and then by adding deionized water to a solids mass fraction of 75% (2 g, 1 h 120 ° C , Glass bowl). The pH of the resin solution was adjusted to 10 by adding dilute sodium hydroxide solution. 965 g of resin with a solids mass fraction of 75%, a viscosity at 23 ° C. of 2620 mPa · s and an unlimited compatibility (miscibility) with deionized water were obtained. The content of unreacted sodium disulfite, based on the amount of melamine, is about 27.5 mmol / mol after titration with iodine / starch, ie only about 14% of the sodium disulfite used is freely available in the resin.

Example 3:

The procedure was as described in Example 1, with the exception that the aqueous 40% sodium sulfamate solution only after the melamine has been dissolved, i.e. after 10 minutes Stirring at 95 ° C was added. 955 g of a resin solution with a Solid mass fraction of 75%, an unlimited compatibility (miscibility) with deionized water, a viscosity at 23 ° C of 2530 mPa · s and a mass fraction obtained free formaldehyde of 0.14%.

Comparative Example 1:

In a 4 1 three-necked flask equipped with a stirrer, reflux condenser and internal thermometer 79 g of deionized water and 541 g (3.9 x 1.8 mol) of a 39% aqueous formaldehyde solution submitted and heated to 85 ° C. Then 3.9 ml of 2.0 N (3.9 x 2.0 mmol) Sodium hydroxide solution - a pH of approx.8.4 was established - and immediately afterwards 492 g (3.9 mol) Melamine added. The approach is supported by the heat of reaction within Heated to 95 ° C for 5 minutes and stirred at 95 ° C for a further 10 minutes. Then was cooled to 58 ° C. 2499 g (3.9 x 20.0 mol) of methanol were added to the reaction mixture and 3.25 g (3.9 x 7.0 mmol) of 53% nitric acid were added. This resulted in a pH value of about 6.1 a. The reaction mixture was heated to 50 ° C and at this time Temperature kept under stirring until the reaction mixture is compatible with saturated saline at 20 ° C 1: 5.0 (mass ratio reaction mixture: Saline). The reaction was started by adding 10 ml (3.9 x 5 mmol) of 2N Sodium hydroxide solution and cooling to 30 ° C stopped. The one containing methanol The reaction mixture was on a rotary evaporator at 100 hPa (100 mbar) at a Bath temperature of approx. 60 ° C concentrated and with deionized water to a solid mass fraction of 75% (2 g, 1 h at 120 ° C., small glass dishes). The pH of the Resin solution was adjusted to 10 by adding dilute sodium hydroxide solution. There were 1030 g of resin with a solids mass fraction of 75%, a viscosity at 23 ° C of 468 mPa · s and unlimited miscibility (compatibility) with deionized water receive. However, the resin became already after 17 days of storage at room temperature (20 ° C) cloudy.

Comparative Example 2:

In a 1 1 three-necked flask with stirrer, reflux condenser and internal thermometer successively 188 g of deionized water, 313 g (2.4 x 1.7 mol) of a 39% aqueous solution Formaldehyde solution, 1.7 ml 2.0 N (2.4 x 1.4 mmol) sodium hydroxide solution, 107 g (2.4 x 0.15 mol) 40% sodium sulfamate solution and 303 g (2.4 mol) melamine submitted. The The reaction mixture was heated to 94 ° C and stirred at 94 ° C (approx. 5 Minutes) until the approach became clear. Then it was cooled to 80 ° C and up to one Compatibility of the reaction mixture with saturated saline at 20 ° C of 1: 4.0 (Mass ratio reaction mixture: saline) condensed. The reaction was stopped by cooling to 20 ° C. The pH of the mixture was adjusted by adding of dilute sodium hydroxide solution to about 9.5. The resin had a solids mass fraction of 51% and an unlimited miscibility (compatibility) with deidnisized water. However, after only 16 days of storage at 20 ° C Water compatibility to below 1:15 (mass ratio resin: deionized water). After 5.5 weeks the resin became cloudy.

Application examples: Resistance to dry fracture of impregnated glass fleeces

The resin from Example 1 was tested against a commercially available methyl-etherified melamine resin with a molar ratio of formaldehyde building blocks to melamine building blocks (F / M) of 2.3. 65 parts by mass of deionized water and 0.35 parts by mass of 25% phosphoric acid were added to each 10 parts by mass of 75% resin. A strip (16 x 24 cm) of glass filter paper (from Schleicher & Schüll, type GF 8, approx. 75 g / m ² ) was impregnated with this in each case by immersion. The moist impregnate was stripped on both sides using glass rods and dried at 180 ° C. for 3 minutes. The residual moisture was then about 0.5%. The dry fracture resistance, determined on a 1.5 cm wide and 15 cm long test strip, was 32.3 N in the longitudinal direction for the fleece impregnated with resin from Example 1, for the 28.4 N impregnated with the commercially available resin.

Removable formaldehyde

To determine the amount of formaldehyde released during curing, the resin according to the invention from Example 1 was tested in comparison with the resin from Comparative Example 1 and the above-mentioned commercially available methyl-etherified melamine resin. For this purpose, 20 g of the resin in question (75% strength) were mixed with 55 g of deionized water and 2.25 g of 10% strength phosphoric acid. Approx. 1.5 g of this soaking liquor was applied evenly to two strips (4 x 25 cm) of glass filter paper (Schleicher & Schull, type GF 8, approx. 75 g / m ² ), in a tube at 170 ° C and an air flow of 60 l / h of formaldehyde released within 35 minutes.

The following values were found: With resin from Example 1 1.1% based on weighed solid resin With resin from comparative example 1 1.5% based on weighed solid resin With commercially available resin 2.4% based on weighed solid resin

Elimination of formaldehyde under the influence of hydrolysis using the example of an impregnated Glass filter paper (application fleece / textile)

To determine the formaldehyde that can be removed from an end product, the resin according to the invention from Example 1 was tested against the commercially available methyl-etherified melamine resin mentioned above. For this purpose, 10 g of the resin in question (75%) were mixed with 65 g of deionized water and 0.35 g of 25% phosphoric acid and glass filter paper (from Schleicher & Schüll, type GF 8, approx. 75 g / m ² ) in of this liquor so impregnated that the impregnates had a resin content of approx. 20%. 24 sections of the impregnate measuring 2.5 cm x 5.0 cm = 0.030 m ² were suspended above the water level in 500 ml polyethylene bottles, which had previously been filled with 50 ml of deionized water, and during 6, 16 and 24 Leave for hours at 50 ° C. The formaldehyde content in the contaminated water was determined after the test times by converting the formaldehyde with acetylacetone to diacetyldihydrolutidine (DDL) spectrophotometrically at the wavelength 412 nm (optimum of the DDL). The following values were found for the quotient m _F / m _H (in%) of the mass m _{F of} the split off formaldehyde and the mass m _{H of} the solid resin in the sample: Mass of the released formaldehyde based on the mass of the solid resin in% Test time at 50 ° C in hours Resin from Example 1 Commercially available methyl etherified melamine resin 6 0.3 0.4 16 0.7 1.0 24 1.2 1.6

Claims (13)

Water-dilutable etherified melamine-formaldehyde resins, can be produced by Implementation of melamine, formaldehyde, a compound with anionic groups and ethereal alcohol in a molar ratio in the reaction mixture of Melamine: formaldehyde: compound with anionic group: etherification alcohol of 1: (1.7 to 7.0): (0.01 to 0.4): (5 to 30). Water-dilutable etherified melamine-formaldehyde resins according to Claim 1, characterized in that the compounds having anionic groups from salts of the amidosulphuric acid H ₂ N-SO ₂ -OH, the sulfurous acid H ₂ SO ₃ and the disinfectant acid H ₂ S ₂ O ₅ with alkali metals and ammonium are selected. Water-dilutable etherified melamine-formaldehyde resins according to Claim 1, characterized in that up to 10% of the melamine is replaced by one or more compounds selected from acetoguanamine, benzoguanamine, dicyandiamide, caprinoguanamine and the cyclic ureas 2-imidazolidinone, 2-oxohexahydropyrimidine and glycoluril. Water-dilutable etherified melamine-formaldehyde resins according to Claim 1, characterized in that up to 8% of the melamine is replaced by one or more compounds selected from urea and thiourea and dicyandiamide. Water-dilutable etherified melamine-formaldehyde resins according to Claim 1, characterized in that the etherifying alcohol is selected from linear and branched aliphatic alcohols having 1 to 6 carbon atoms. Water-dilutable etherified melamine-formaldehyde resins according to claim 1, characterized in that the etherifying alcohol is methanol. Water-dilutable etherified melamine-formaldehyde resins according to claim 1, characterized in that the compound with anionic groups is selected from the sodium salt of amidosulfuric acid and sodium disulfite. Process for the preparation of water-dilutable etherified melamine-formaldehyde resins, characterized in that in the first stage melamine and formaldehyde are reacted in the presence of a compound with an anionic group under alkaline conditions, and in the second stage the etherified alcohol and an acid is added and the etherification is carried out. A process for the preparation of water-dilutable etherified melamine-formaldehyde resins, characterized in that in the first stage melamine and formaldehyde are reacted under alkaline conditions until the melamine has dissolved, then a compound with an anionic group is added and in the second stage with the reaction product is reacted in the first stage, and in the third stage the etherification alcohol and an acid are added to the resin solution obtained and the etherification is carried out. A method according to claim 8 or 9, characterized in that the etherification is carried out until the compatibility of the resin solution with saturated saline is at least 1: 2.0. Use of the water-dilutable etherified melamine-formaldehyde resins according to claim 1 for the production of impregnates, characterized in that substrates selected from mineral substances, papers and cardboard, and textile structures made of threads or fibers made of glass or natural or synthetic polymers with aqueous solutions of the etherified Melamine-formaldehyde resins are soaked or coated, and the soaked or coated substrates are then dried. Use according to claim 11, characterized in that glass fiber nonwovens are used as the substrate. Use according to claim 11, characterized in that paper is used as the substrate.